U.S. patent number 6,868,620 [Application Number 10/210,291] was granted by the patent office on 2005-03-22 for digital measuring instrument having flexible measuring line.
This patent grant is currently assigned to Solar Wide Industrial, Ltd.. Invention is credited to Hughes Sanoner.
United States Patent |
6,868,620 |
Sanoner |
March 22, 2005 |
Digital measuring instrument having flexible measuring line
Abstract
A digital measuring instrument includes a housing containing a
measuring line, a rotatable drum engaging the line whereby movement
of the line causes rotation of the drum, a storage spool mounted in
the housing for storing the line, a crank assembly for rotating the
storage spool for winding the measuring line about the storage
spool, and a rotatable disc that rotates simultaneously with the
measuring drum. The instrument includes an optical sensor in
communication with the rotatable disk for compiling data related to
rotation of the disk, and electronic circuitry in communication
with the optical sensor for calculating a length of the line drawn
from the housing. The housing has a well for receiving the storage
spool and a side cover with a slideable lock for covering the
well.
Inventors: |
Sanoner; Hughes (Hong Kong,
CN) |
Assignee: |
Solar Wide Industrial, Ltd.
(HK)
|
Family
ID: |
31975956 |
Appl.
No.: |
10/210,291 |
Filed: |
August 1, 2002 |
Current U.S.
Class: |
33/763; 33/756;
33/769 |
Current CPC
Class: |
G01B
3/11 (20130101); G01B 3/1094 (20200101); G01B
3/1069 (20200101) |
Current International
Class: |
G01B
3/11 (20060101); G01B 3/10 (20060101); G01B
3/02 (20060101); G01B 003/10 () |
Field of
Search: |
;33/762,763,756,755,759,761,767,768,769,770 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bennett; G. Bradley
Assistant Examiner: Smith; R. Alexander
Attorney, Agent or Firm: Lerner, David, Littenberg, Krumholz
& Mentlik, LLP
Claims
What is claimed is:
1. A hand-held digital measuring instrument comprising: a housing
containing a measuring line; a rotatable measuring drum in
engagement with said measuring line so that movement of said
measuring line causes rotation of said measuring drum; a storage
spool mounted in said housing for storing said measuring line; a
crank assembly having a crank handle coupled with said storage
spool for rotating said storage spool for winding said measuring
line about said storage spool; a rotatable disc coupled with said
measuring drum for rotating simultaneously with said measuring
drum; an optical sensor in communication with said disk for
compiling data related to rotation of said disk; electronic
circuitry in communication with said optical sensor for processing
the compiled data so as to calculate a length of said measuring
line drawn from said housing; said housing including a well adapted
to receive said storage spool; and a removable side cover
attachable to said housing over said well, said side cover
including a slideable lock for selectively detaching said side
cover from said housing for uncovering said well, wherein said
storage spool is rotatable for winding and unwinding said measuring
line from said storage spool.
2. The digital measuring instrument as claimed in claim 1, wherein
said optical sensor includes a light generating element opposed by
a light sensing element that is adapted to sense light emitted from
said light generating element.
3. The digital measuring instrument as claimed in claim 2, wherein
said disc has a plurality of teeth at a peripheral edge thereof
that pass between said light generating element and said light
emitting element during rotation of said disc.
4. The digital measuring instrument as claimed in claim 3, wherein
said plurality of teeth are evenly spaced from one another by gaps
extending therebetween.
5. The digital measuring instrument as claimed in claim 4, wherein
said optical sensor generates a first signal when one of said teeth
blocks said light from reaching said light sensing element and a
second signal when said light is detected by said light sensing
element after passing through one of said gaps.
6. A hand-held digital measuring instrument comprising: a housing
containing a rotatable storage spool; a measuring line windable
about said storage spool; a measuring drum rotatably mounted in
said housing and including a surface in contact with said measuring
line, wherein movement of said measuring line causes rotation of
said measuring drum; a disc coupled with said measuring drum,
wherein rotation of said measuring drum causes simultaneous
rotation of said disc; an optical sensor in communication with said
disc for compiling data related to rotation of said disc; and
electronic circuitry in communication with said optical sensor for
processing said compiled data so as to calculate a length of said
measuring line drawn from said housing; and a front cover hingeably
connected to said housing, said front cover including an opening
through which said measuring line is drawn from said housing and a
cutting element for selectively cutting said measuring line.
7. The digital measuring instrument as claimed in claim 6, wherein
said housing includes a digital display adapted to display the
calculated length of said measuring line drawn from said
housing.
8. The digital measuring instrument as claimed in claim 6, wherein
said disc includes a peripheral edge having a plurality of teeth
evenly spaced from one another.
9. The digital measuring instrument as claimed in claim 8, wherein
said teeth define evenly spaced gaps therebetween.
10. The digital measuring instrument as claimed in claim 8, wherein
said optical sensor is in substantial alignment with said teeth of
said disc.
11. The digital measuring instrument as claimed in claim 10,
wherein said optical sensor includes a light generating element
directed toward a first face of said disc and a light sensing
element directed toward a second face of said disc, wherein said
light generating element and said light sensing element oppose one
another and are in substantial alignment with one another.
12. The digital measuring instrument as claimed in claim 11,
wherein said disc is aligned with said light generating and light
sensing elements so that said teeth of said disc pass between said
light generating element and said light sensing element.
13. The digital measuring instrument as claimed in claim 12,
wherein said light generating element is a light emitting diode
(LED) and said light sensing element is a phototransistor.
14. The digital measuring instrument as claimed in claim 13,
wherein said phototransistor generates a first pulse signal when
light from said light generating element passes through one of said
gaps between said teeth of said disc and a second pulse signal when
said light from said light generating element is blocked from
reaching said light sensing element by one of said teeth of said
disc.
15. The digital measuring instrument as claimed in claim 6, further
comprising a printed circuit board including said electronic
circuitry, wherein said electronic circuitry is analog
circuitry.
16. The digital measuring instrument as claimed in claim 6, further
comprising a printed circuit board including said electronic
circuitry, wherein said electronic circuitry is digital
circuitry.
17. The digital measuring instrument as claimed in claim 6, further
comprising a microprocessor having one or more routines stored
therein for operating said electronic circuitry.
18. The digital measuring instrument as claimed in claim 6, wherein
said measuring line is flexible.
19. The digital measuring instrument as claimed in claim 6, wherein
said measuring line is made of a material selected from the group
consisting of cotton, metal synthetic material, nylon and
polyester.
20. The digital measuring instrument as claimed in claim 6, wherein
said measuring line is made of stainless steel.
21. The digital measuring instrument as claimed in claim 6, wherein
said measuring line wound about said storage spool has a length of
approximately 750-1500 m.
22. The digital measuring instrument as claimed in claim 6, wherein
said housing includes a handle integrally formed therewith.
23. The digital measuring instrument as claimed in claim 6, further
comprising a crank handle coupled with said storage spool for
winding said measuring line around said storage spool.
24. The digital measuring instrument as claimed in claim 6, wherein
said housing includes a well adapted to receive said storage spool
and a removable side cover attachable to said housing over said
well.
25. The digital measuring instrument as claimed in claim 24,
wherein said side cover includes a slideable lock movable for
detaching said side cover from said housing for selectively
uncovering said well.
26. The digital measuring instrument as claimed in claim 6, further
comprising a brake coupled with said storage spool for selectively
locking said storage spool from rotating.
27. The digital measuring instrument as claimed in claim 6, further
comprising a measuring drum assembly including said measuring drum,
said measuring drum being mounted on a shaft carrying a first gear,
wherein said first gear is mechanically coupled with a second gear
which, in turn, is coupled with said disc so that rotation of said
measuring drum causes rotation of said disc.
28. The digital measuring instrument as claimed in claim 27,
wherein said measuring drum assembly includes at least one
stationary guide, at least one roller guide and at least one
cleaner guide.
29. The digital measuring instrument as claimed in claim 28,
wherein said measuring drum assembly defines a threaded path for
said measuring line as said measuring line passes between said
storage spool and said opening of said housing.
30. The digital measuring instrument as claimed in claim 29,
wherein said measuring drum assembly maintains a section of said
measuring line under tension and in engagement with the non-slip
surface of said measuring drum.
31. A hand-held electronic measuring instrument comprising: a
housing adapted to store a measuring line, said housing having a
front cover with an opening for drawing said measuring line from
said housing, said front cover including a cutting element for
selectively cutting said measuring line; a measuring drum mounted
in said housing and including a surface in engagement with said
measuring line, wherein movement of said measuring line rotates
said measuring drum; a disc coupled with said measuring drum for
rotating simultaneously with said measuring drum; an optical sensor
in communication with said disc for recording data related to
rotation of said disc; and electronic circuitry in communication
with said optical sensor for processing the recorded data so as to
calculate a length of said measuring line passing through the
opening of said housing.
32. The electronic measuring instrument as claimed in claim 31,
further comprising: a storage spool rotatably mounted in said
housing for receiving said measuring line; a crank handle connected
with said storage spool for rotating said storage spool so as to
wind said measuring line about said storage spool; and a handle
integrally connected with said housing, wherein said front cover is
hingeably connected to said housing.
33. The electronic measuring instrument as claimed in claim 31,
further comprising a printed circuit board containing said
electronic circuitry.
34. The electronic measuring instrument as claimed in claim 31,
wherein said electronic circuitry is adapted to recalibrate for
said measuring line when said measuring line is made of different
materials.
35. The electronic measuring instrument as claimed in claim 31,
further comprising data entry keys for controlling operation of
said electronic circuitry.
Description
FIELD OF THE INVENTION
The present invention is related to tape measures used for
measuring distances and is specifically related to electronic tape
measures.
BACKGROUND OF THE INVENTION
Tape measures have been used for many years to accurately measure
distances between two points and the lengths of objects. Tape
measures typically include a housing having an opening through
which a measuring tape is drawn. The measuring tape has indicia
printed thereon that are used to measure distances. When measuring
a distance, the measuring tape is unwound from a storage spool as
it is drawn through the opening of the housing. When the measuring
task is complete, the measuring tape is rewound onto the storage
spool.
In recent years, electronic tape measures have been developed which
electronically track the length of a measuring tape unwound from a
storage spool. Electronic tape measures typically include a reading
element in communication with the storage spool that generates
electric pulses corresponding to the length of the measuring tape
drawn from the spool. The electric pulses are counted by
operational circuitry, which converts the pulses into a digital
readout provided on a visual display.
One electronic tape measure is disclosed in U.S. Pat. No. 5,142,793
to Crane which teaches a housing, a reel located within the housing
and a measuring tape wound on the reel. The measuring tape is
extendable through an opening in the housing as the reel is
unwound. A first measuring element is associated with the reel for
generating incremental measuring data and a second measuring
element generates absolute measuring data as the measuring tape is
extended. A processor responsive to both the incremental measuring
data and the absolute measuring data generates an output that
reflects the linear extension of the measuring tape from the
housing. The device also includes a visual display for showing
information related to the linear extension of the measuring
tape.
U.S. Pat. No. 5,426,863 to Biggel discloses a combination tape
measure and calculator. The tape measure includes a measuring tape
having equally spaced holes along the length thereof. The holes are
read by closely spaced optical readers arranged to generate
incremental unit signals that are transmitted to a microprocessor
mounted in a case.
U.S. Pat. No. 5,433,014 to Falk et al. discloses a digital tape
measure including a transmitter for transmitting measurements to a
remote location. The tape measure includes a housing, a measuring
tape having a series of optical markings, an optical sensor for
sensing the optical markings when the tape is extended or
retracted, a logic circuit in communication with the optical sensor
for providing a digital signal representative of the length of the
tape drawn from the housing, and a transmitter connected to the
logic circuit for transmitting the digital signal to the remote
location. A receiving unit is provided at the remote location for
receiving, storing and displaying the measurements.
U.S. Pat. No. 5,286,972 to Falk et al. discloses a photoelectric
measuring device with a digital display. The measuring device
measures distance by optically scanning the length of a line as it
is unwound from a reel. The line is provided with a plurality of
dye marks placed at spaced intervals. The dye marks are detected by
an optical sensor in communication with a circuit that maintains a
count indicative of the length of the line. The count is displayed
on an LED display.
The above-described devices generally use measuring tapes having a
substantial width and thickness that limits the length of tape,
such as 100 meters or less, that can be conveniently stored on a
single spool. Tape measures having distances of over one hundred
meters are rare because longer tapes will substantially increase
the overall size of the tape measure housing, thereby making the
tape measure extremely bulky and burdensome to operate.
Another problem with conventional tape measures relates to
maintenance and replacement costs. Tape measures are frequently
damaged because they are used in harsh environments resulting in
the measuring tape being damaged. A damaged measuring tape cannot
accurately measure a distance or cannot be rewound onto a storage
spool. As a result, the measuring tape must be repaired or replaced
at substantial cost. In many instances, a brand new tape measure
must be purchased.
Another problem relates to the accuracy of electronic tape
measures. Many conventional electronic tape measures are inaccurate
or unreliable because they don't account for the hanging radius of
the measuring tape on the storage spool as the tape is unwound from
the storage spool.
Thus, there is a need for an electronic tape measure that enables
users to measure longer distances. There is also a need for a
durable electronic tape measure, which allows the measuring element
extended from a housing to be easily replaced, at low cost. There
is also a need for an electronic tape measure that is accurate and
reliable.
SUMMARY OF THE INVENTION
In accordance with certain preferred embodiments of the present
invention, a digital tape measure includes a housing containing a
rotatable storage spool, and a measuring line windable about the
storage spool. The tape measure also preferably includes a
measuring drum rotatably mounted in the housing and including a
surface in contact with the measuring line, whereby movement of the
measuring line causes rotation of the measuring drum. A disc is
desirably coupled with the measuring drum, whereby rotation of the
measuring drum due to movement of the measuring line causes
simultaneous rotation of the disc. The digital tape measure also
includes an optical sensor in communication with the disc for
compiling data related to rotation of the disc, and electronic
circuitry in communication with the optical sensor for processing
the compiled data so as to calculate a length of the measuring line
drawn from the housing. The housing preferably includes a visual
display, such as a digital display, adapted to show the calculated
length of the measuring line that has been drawn from the
housing.
The disc is preferably a circular disc that is rotatable about a
shaft. The shaft preferably links the disc with the rotatable
measuring drum. The disc preferably includes a peripheral edge
having a plurality of evenly spaced teeth. The teeth desirably
define evenly spaced gaps therebetween. When the disc is inserted
into the housing of the digital tape measure, the teeth of the disc
are preferably in substantial alignment with the optical sensor. As
a result, the rotating teeth are in alignment with the optical
sensor.
The optical sensor of the present invention desirable includes a
light generating element such as a light emitting diode, directed
toward a first face of the rotating disc, and a light sensing
element, such as a photo sensor, directed toward a second face of
the disc. The light-generating element and the light sensing
element preferably oppose one another and are in substantial
alignment with one another. As the disc rotates, the optical sensor
generates a first signal when the light from the light generating
element reaches the light sensing element. When the disc rotates so
that one of the teeth is aligned between the light generating
element and the light-sensing element, the optical sensor generates
a second signal indicating such a condition. As a result, the
optical sensor generates a first pulse signal when light from the
light generating element passes through one of the gaps between the
teeth of the disc to reach the light sensing element, and a second
pulse signal when light from the light generating element is
blocked from reaching the light sensing element by one of the teeth
of the disc.
The digital tape measure desirably includes a printed circuit board
including electronic circuitry in communication with the optical
sensor. The electronic circuitry is selected from the group
consisting of analog circuitry and digital circuitry. The printed
circuit board also preferably includes one of more microprocessors
having one of more subroutines stored therein for operating the
electronic circuitry. The electronic circuitry preferably operates
in conjunction with software that enables a user to re-calibrate
the unit for different types of line diameters and/or line
materials. The calibration data is permanently stored in memory,
even when battery power is out and even if battery power is not
used. As a result, a user may change the measuring line to use a
line having a different diameter or material, and then re-calibrate
the unit to work accurately with the new measuring line. In certain
preferred embodiments, the software is adapted to count pulses for
a predetermined length of measuring line that passes the optical
sensor. In one particular preferred embodiment, the software is
adapted to count two (2) pulses for each 1 mm (0.04") of measuring
line, thereby ensuring maximum precision and accuracy.
The measuring line drawn from the storage spool is preferably
flexible. In certain preferred embodiments, the measuring line is
made from a material selected from the group consisting of cotton,
metal and synthetic materials such as nylon and polyester. In one
preferred embodiment, the measuring line is string. In another
preferred embodiment, the measuring line is made of stainless
steel. The measuring line is wound about the storage spool and has
a length of approximately 750 to 1500 meters. Although not limited
by any particular theory of operation, it is believed that using a
measuring line, as opposed to a wide measuring tape, enables a
longer length of measuring material to be wound about a storage
spool. As is well known to those skilled in the art, a conventional
measuring tape has substantial thickness and width that occupies a
substantial amount of space on a storage spool. This dramatically
limits the length of measuring tape that may be stored in a hand
carried tape measure. In contrast, the present invention provides
an elongated, flexible measuring line that has minimal width and
thickness. As a result, a substantially longer length of material
may be wound about a storage spool, thereby maximizing the distance
that can be measured using the present invention.
In certain preferred embodiments, the housing includes a hingeable
front cover having a button that may be depressed for allowing the
front cover to be swung from a closed position to an open position.
In the open position, an interior region of the housing may be
accessed. The present invention also desirably includes a crank
assembly including a crank handle. The crank assembly is coupled
with the storage spool for providing an element for rewinding the
measuring line about the storage spool.
In certain preferred embodiments, the housing includes a well
adapted to receive the storage spool and a removable cover
securable over the well. The side cover includes a lock for
selectively uncovering the well. As a result, a storage spool
having worn or damaged measuring line wound about it may be
replaced with another storage spool having new or repaired
measuring line. Thus, the removable side cover enables a
replacement storage spool with measuring line to be quickly and
easily installed in the housing.
The present invention also preferably includes a measuring drum
assembly including the measuring drum, whereby the measuring drum
is mounted on a shaft carrying a first gear that is mechanically
coupled with the rotating disc in communication with the optical
sensor. The measuring line is threaded through the measuring drum
assembly so that movement of the measuring line causes simultaneous
rotation of the measuring drum. Due to the gear and shaft linkages
described above, rotation of the measuring drum causes simultaneous
rotation of the disc. In certain preferred embodiments, the
measuring drum includes at least one stationary guide, at least one
roller guide, and at least one cleaner guide for cleaning an
exterior surface of the line. For example, if the measuring line is
made of cotton, the cleaner guide may remove extraneous matter
present at an outer surface of the measuring line. Thus, the
measuring drum assembly defines a threaded path for the measuring
line as the measuring line passes between the storage spool and the
opening in the hingeable front cover of the housing. The measuring
drum assembly preferably maintains at least a section of the
measuring line in non-slip engagement with the surface of the
measuring drum, and maintains the measuring line under tension. As
used herein, the term "non-slip surface" means that there will be
no slippage between movement of the measuring line and the outer
annular surface of the measuring drum.
Other preferred embodiments of the present invention disclose an
electronic measuring device having a flexible measuring line
including a housing having an opening for the measuring line, a
storage spool rotatably mounted in the housing for storing the
measuring line, and a measuring drum rotatably mounted in the
housing and including a surface in contact with the measuring line,
whereby movement of the measuring line through the opening of the
housing causes rotation of the measuring drum. The electronic
measuring device also desirably includes a disc coupled with the
measuring drum for rotating simultaneously with the measuring drum,
an optical sensor in communication with the disc for generating
signals related to rotation of the disc, and electronic circuitry
in communication with the optical sensor for processing the
generated signals so as to calculate a length of the measuring line
passing through the opening of the housing.
Other preferred embodiments of the present invention include an
electronic tape measure comprising a housing adapted to store
measuring line, the housing having an opening for drawing the
measuring line from the housing, and a measuring drum mounted in
the housing and including a non-slip surface in engagement with the
measuring line, wherein movement of the measuring line rotates the
measuring drum. The electronic tape measure also includes a disc
coupled with the measuring drum for rotating simultaneously with
the measuring drum, an optical sensor in communication with the
disc for recording data related to rotation of the disc, and
electronic circuitry in communication with the optical sensor for
processing the recorded data so as to calculate a length of the
measuring line passing through the opening of the housing. This
particular embodiment also preferably includes a storage spool
rotatably mounted in the housing for receiving the measuring line,
and a crank assembly connected with the storage spool for rotating
the storage spool so as to wind the measuring line about the
storage spool.
Still other preferred embodiments of the present invention include
a digital tape measure having a housing containing a measuring
line, and a rotatable measuring drum in engagement with the
measuring line so that movement of the measuring line causes
rotation of the measuring drum. The digital tape measure also
desirably includes a rotatable disc coupled with the measuring drum
for rotating simultaneously with the measuring drum, an optical
sensor in communication with the disc for compiling data related to
rotation of the disc, and electronic circuitry in communication
with the optical sensor for processing the compiled data so as to
calculate a length of the measuring line drawn from the housing.
The optical sensor desirably includes a light-generating element
opposed by a light-sensing element that is adapted to sense light
emitted from the light-generating element. The optical sensor
desirably generates a first signal when light from the
light-generating element reaches the light-sensing element, and a
second signal when the light from the light-generating element is
blocked by one of the teeth of the disc.
These and other preferred embodiments of the present invention will
be described in more detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a side view of a digital tape measure, in accordance
with certain preferred embodiments of the present invention.
FIG. 2 shows a partially exploded view of the digital tape measure
shown in FIG. 1.
FIG. 3 shows a cross-sectional view of the digital tape measure
shown in FIGS. 1 and 2, including an optical sensor secured in a
housing.
FIG. 4 shows a front end view of the optical sensor shown in FIG.
3.
FIG. 5 shows a bottom view of the optical sensor shown in FIG.
4.
FIG. 6 shows a sectional view of the optical sensor taken along
line VI--VI of FIG. 5.
FIG. 7A shows an exploded view of measuring drum assembly for a
digital tape measure, in accordance with certain preferred
embodiments of the present invention.
FIG. 7B shows the measuring drum assembly of FIG. 7A in a partially
assembled state with a measuring line threaded therethrough.
FIG. 7C shows a perspective view of the measuring drum assembly of
FIG. 7A in a fully assembled state.
FIG. 8 shows an expanded view of a stationary guide for a measuring
line, in accordance with certain preferred embodiments of the
present invention.
FIG. 9 shows a top plan view of a control panel for a digital tape
measure, in accordance with certain preferred embodiments of the
present invention.
FIG. 10 shows a perspective view of the digital tape measure shown
in FIG. 9.
FIGS. 11A-11D show subroutines for operational circuitry of a
digital tape measure, in accordance with certain preferred
embodiments of the present invention.
FIG. 12 shows a schematic of electronic circuitry of used to
perform the subroutines shown in FIGS. 11A-11D.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
FIG. 1 shows a digital tape measure 20 including a housing 22
having a front 24, a rear 26, atop a bottom 30. In certain
preferred embodiments, housing 22 is made of molded plastic.
Housing 22 includes a hingeable front cover 32 movable between open
and closed positions. Hingeable front cover 32 includes a cutting
element 36 attached thereto for selectively cutting or trimming a
measuring line (not shown). Hingeable front cover 32 includes an
opening 38 through which the measuring line can be drawn from
housing 22.
Housing 22 also includes a handle 40 that extends along rear 26
between the top and bottom 28, 30 of housing 22. Handle 40 is
preferably integrally molded with the housing 22. A gripping
surface 42 is preferably secured over an exterior surface of handle
40 for improving the gripability of the handle. The handle 40 also
preferably includes one or more finger grooves 44 for enhancing a
user's grip.
Housing 22 preferably includes a first molded part 46 and a second
molded part 48 that are assembled together and held together by
screws 50, 50A, 50B and 50C passed through openings 52A, 52B and
52C formed in first molded part 46. Screws 50A-50C are preferably
anchored in threaded apertures (not shown) formed in second molded
part 48 for reliably securing first and second molded parts 46, 48
together.
Housing 22 also preferably includes a battery compartment cover 54
that selectively closes a battery compartment opening 55 at a lower
end of handle 40. Housing 22 also preferably includes a removable
side cover 56 that covers a well formed in housing 22 that is
adapted to receive a measuring line storage spool (not shown).
Removable side cover 56 includes a slidable lock 58 that may be
urged towards a central knob 60 for releasing side cover 56 from
its attachment with housing 22.
FIG. 2 shows a partially exploded view of the digital tape measure
of FIG. 1, after hingeable front cover 32 has been opened and side
cover 56 (FIG. 1) has been detached from housing 22. The well 62 is
adapted to receive a storage spool 64 having measuring line 66
wound thereon. Spool 64 has a central opening 68 that is mounted
over spool gear 69 having a central shaft 70 and spaced projections
72 that are engageable with similarly shaped, spaced depressions
(not shown) formed on an underside of storage spool 64. The spaced
projections 72 provide positive alignment of storage spool 64 with
gear 74.
Digital tape measure 20 also includes a measuring drum assembly 76
insertable into the front 24 of housing 22 when hingeable front
cover 32 is in the open position shown in FIG. 2. As will be
described in more detail below, measuring drum assembly 76 is
designed to receive a free end of measuring line 66 supplied from
storage spool 64. Measuring drum assembly 76 includes a series of
guides for threading the measuring line 66 therethrough. Housing 22
also includes a stationary guide 78 having an opening 80 extending
therethrough for engaging and guiding the measuring line 66 after
the measuring line has passed through a front end of measuring drum
assembly 76.
The digital measuring tape also includes an optical sensor 82
including a light generating element 84 and a light sensing element
86 that are directed towards one another on opposite faces of a
rotatable disc 88 having teeth 90 at the periphery thereof and gaps
92 between the teeth 90. The teeth 90 are preferably evenly spaced
from one another.
Hingeable front cover 32 includes a depressible button 96 and a
projection 98 integrally connected to button. When button 96 is
depressed, projection 98 moves in an arcuate path shown by arrow
A.sub.1. When hingeable front cover 32 is moved in a clockwise
direction toward the top 28 of housing 22, projection 98 is
securable under locking bar 100 for holding hingeable front cover
32 in the closed position. In order to open hingeable front cover
32 once again, button 96 is depressed so as to uncouple projection
98 from engagement with locking bar 100.
Digital measuring tape 20 also includes a printed circuit board 102
secured within housing 22. The printed circuit board 102 preferably
includes microelectronic elements (not shown) such as
microprocessors and memory devices for controlling electronic
circuitry coupled with printed circuit board 102. The printed
circuit board 102 is preferably in communication with optical
sensor 82 for obtaining data from optical sensor 82 when disc 88
rotates as measuring line 66 is drawn through the opening 38 of
hingeable cover 32.
Referring to FIG. 3, digital tape measure 20 also includes a brake
104 having a pivotable brake knob 106 with an underside 108 coupled
with a first end 110 of a first lever 112. First lever 112 also
includes a lower end 114 coupled with a second lever 116. The
second lever 116 has a lower end with teeth 118 with teeth that
mesh with crank assembly gear 120 having teeth 122. The brake knob
106 is pivotable between a first unlocked position and a second
locked position. In the first unlocked position, the teeth 118 of
second lever 116 are remote from the teeth 122 of crank assembly
gear 120 so that crank assembly gear is free to rotate. In a second
locked position shown in FIG. 3, the teeth 118 of second lever 116
engage the teeth 122 of crank handle gear 120 so that crank handle
gear 120 cannot rotate. In operation, the brake 104 is movable back
and forth between the first unlocked position and the second locked
position for selectively locking movement of the crank handle gear
120.
FIG. 3 also shows rotatable disc 88 mounted in housing 22 for
rotating in response to movement of a measuring drum, as will be
described in more detail below. The teeth 90 at the periphery of
disc 88 are designed to pass between light generating element 84
and light sensing element 86 of optical sensor 82. Optical sensor
82 is preferably in communication with printed circuit board 102
via communication line 124.
FIGS. 4 and 5 show a front end view of optical sensor 82 including
light generating element 84 and light sensing element 86. Disc 88
is provided between light generating element 84 and light sensing
element 86. Disc 88 has a first face 126 facing toward light
generating element 84 and a second face 128 facing toward light
sensing element 86. The teeth 90 at the periphery of disc 88 are
adapted to pass between the light-generating element 84 and the
light-sensing element 86 as disc 88 rotates.
FIG. 6 shows the teeth 90 of disc 88 passing by light generating
element 84. When one of the gaps 91 of disc 88 is aligned between
the light generating element and the light-sensing element, light
generated by light generating element 84 is able to pass through
the gap 91 and be sensed by light sensing element 86 (not shown).
When one of the teeth 90 is positioned between the light generating
element and the light sensing element, as shown in FIG. 6, the
light emitted from the light generating element 84 is not sensed by
the light sensing element. In operation, optical sensor 82
generates a first signal when the light passes through one of the
gaps 91 and a second signal when the light is blocked by one of the
teeth 90. The first and second signals are processed by the
operational circuitry to determine the length of the measuring line
drawn from the housing.
FIG. 7A shows an exploded view of a measuring drum assembly 76, in
accordance with certain preferred embodiments of the present
invention. Measuring drum assembly 76 includes a base member 130
and a cap 132 securable over the base member. The base member 130
includes a centrally located well 134 adapted to receive measuring
drum 136 having an annular surface 138 adapted to engage the
measuring line unwound from the storage spool (FIG. 2). The
measuring drum 138 includes a central hub 140 having an opening 142
adapted to receive shaft 144. Shaft 144 has a lower end (not shown)
passable through an opening 146 in the bottom of well 134 for
supporting rotation of measuring drum 136, and an upper end 148
having a drive gear 150 mounted thereon. The drive gear 150 rotates
at the same rate as measuring drum 136. A bearing 152, mountable at
the upper end 148 of shaft 144 is insertable into a top wall
aperture 154 of cap 132.
Referring to FIGS. 2 and 7A, base member 130 includes an upstream
end 156 and a downstream end 158. When the measuring drum assembly
76 is secured within the housing 22, the upstream end 156 is
positioned adjacent the stationary guide 78 and the downstream end
148 is positioned adjacent the opening 38 of hingeable front cover
32 when the hingeable front cover is in the closed position. Base
member 130 includes a first stationary line guide 160 securable in
U-shaped groove 162 and a first line cleaner guide 164 securable in
cup 166. Bottom assembly 130 also includes two roller guides 168,
170 for guiding movement of the measuring line. Base assembly 130
also includes a second stationary guide 172 securable in second
U-shaped groove 174, a second line cleaner guide 176 secured in a
second cup 178 adjacent the downstream end 158 of base member 130,
and a third stationary guide 179 between the second stationary
guide 172 and second line cleaner guide 176.
FIG. 7B shows measuring line 66 threaded through the base member
130 of measuring drum assembly 76. The measuring line is drawn from
storage spool 64. The measuring line is threaded in the following
pattern: first stationary line guide 160, first line cleaner guide
164, first roller guide 168, wrapped approximately one and
two-thirds times around measuring drum 136, around second roller
guide 170, through second stationary line guide 174, through third
stationary line guide 175 and through second line cleaner guide 176
at downstream end 158. The measuring line 66 is then passed through
the opening 38 in hingeable front cover 32 (FIG. 3).
Referring to FIGS. 7A and 7C, after the measuring line 66 has been
threaded through the measuring drum assembly 76, the top cover 132
and base member 130 are assembled together, such as by snap-fitting
the top cover 132 and base member 130 together. The fully assembled
measuring drum assembly 76 is insertable into the front end of
housing 22 as shown in FIG. 2.
FIG. 8 shows an expanded view of the stationary guide 78 shown in
FIG. 2. The stationary guide 78 includes an opening 80 that
provides a guide for the measuring line (not shown) between the
storage spool and the upstream end 156 of measuring drum assembly
76 when the measuring drum assembly is inserted into housing
22.
FIG. 9 shows a plan view of the top 28 of housing 22. The housing
22 includes hingeable front cover 32 and depressable button 96 for
enabling hingeable front cover to be swung away from a front end of
housing 22. Hingeable front cover also includes opening 38 that
enables measuring line 66 to be drawn therethough.
The housing 22 has a visual display 180 such as a liquid crystal
display. Visual display 180 includes a main readout 182 providing a
six-digit numeric with comma and decimal point for decimals. The
main readout 182 provides current measuring line readings and
displays the value of memory and recall locations. Visual display
180 also includes a negative sign 184 that is displayed when the
value on the main readout 182 is negative. The negative sign
indicates that the measuring line is retracted from a "rezero"
position. Visual display 180 also includes a memory indicator 186
that is displayed when memory is selected. The memory indicator 186
indicates which of the 15 memory storage locations is being used
and when all of the 15 memory locations are "full." At that point,
a prompt "overwrite? Y/N" indicator 188 will illuminate. If a user
desires to overwrite the previously stored memory at that memory
location, the user will press the yes button below.
The visual display also includes a recall indicator 190 that is
displayed when recall is selected. The recall indicator 190
indicates the last stored measurement and the corresponding memory
location (1-15). Pressing the recall button again will step through
to the next measurement stored in memory. Visual display 180 also
includes location indicator 192 that displays the storage location
of the saved value or the recall value in memory. Visual display
180 also has a sound activated indicator 194 that indicates when
the sound function has been toggled to the "on" position. Unit
indicator 196 denotes the type of units that are being displayed in
the main readout 182. Rezero indicator 198 displays when the
"On/Zero" button is pressed to rezero the display. Overwrite option
indicator 188 is illuminated in the event that a user attempts to
save a measurement in an occupied memory location. At that point,
the user is prompted to confirm the action with the overwrite
option indicator 188. Once a "yes" or "no" is selected, the
overwrite option indicator is turned off.
The visual display 180 also includes an add indicator, represented
by the "+" sign 200, that confirms that the user is in the "add"
mode. Low battery indicator 202 illuminates when battery voltage is
below a predetermined level, such as 4.8 volts. Overspeed indicator
204 illuminates when the digital tape measure will not function
properly due to the measuring line 66 moving at a speed of over 10
feet per second. If the overspeed indicator 204 illuminates, a user
should remeasure a length, while insuring that the measuring line
does not move at a speed of over 10 feet per second. The
calibration indicator 206 is displayed when the "On/Zero" button is
depressed and held for five seconds. At that point, the digital
tape measure 20 enters calibration mode.
Digital tape measure 20 also includes a series of data entry keys
for controlling operation of the device. The data entry keys
include add button 208, Clear/No button 210, unit button 212,
recall button 214, Enter/Yes button 216, sound activating button
218, memory storage button 220 and On/Zero button 222. The housing
22 also includes brake button 106 that may be toggled back and
forth between a locked position and an unlocked position in which
the measuring line 66 can be drawn from the housing 22.
Referring to FIGS. 9 and 10, the tape measure also includes a crank
assembly 224 having a crank handle 226 that is coupled with the
storage spool gear 69 for rotating storage spool 64 to wind
measuring line 66 about storage spool 64. When the brake assembly
106 is moved into the locking position, the crank assembly 224 is
locked in place, thereby preventing further movement of the
measuring line.
FIGS. 11A-11D show preferred logic subroutines used for operating
the digital tape measure. FIG. 12 shows electronic circuitry
mounted atop the printed circuit board (FIG. 2) for performing the
steps shown in the logic subroutines of FIGS. 11A-11D.
Although the invention herein has been described with reference to
particular embodiments, it is to be understood that these
embodiments are merely illustrative of the principles and
applications of the present invention. It is therefore to be
understood that numerous modifications may be made to the
embodiments described herein and that other arrangements may be
devised without departing from the spirit and scope of the present
invention as defined by the appended claims.
* * * * *